Pneumocystis carinii is a prevalent opportunistic fungal infection striking HIV-afflicted hosts. The cell wall of P. carinii is proving to be structurally more complex than previously thought. We have purified, by preparatory SDS-PAGE, a family of glycoproteins from P. carinii cell wall material isolated by Zymolyase [?(1.3)-glucanase] treatment. We are in the process of characterizing these cell wall glycoproteins with a number of MS-based approaches.